MC68HC908GT16_07 Datasheet, PDF (43/292 Pages) Freescale Semiconductor, Inc – Microcontrollers

Flash Memory
performed in the order as shown, but other unrelated operations may occur
between the steps.
CAUTION
A mass erase will erase the internal oscillator trim values at $FF80 and
$FF81.
2.6.5 Flash Program/Read Operation
Programming of the Flash memory is done on a row basis. A row consists of 32 consecutive bytes starting
from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, or $XXE0. Use the following
step-by-step procedure to program a row of Flash memory
Figure 2-4 is a flowchart of the programming algorithm.
NOTE
Only bytes which are currently $FF may be programmed.
1. Set the PGM bit. This configures the memory for program operation and enables the latching of
address and data for programming.
2. Read the Flash block protect register.
3. Write any data to any Flash location within the address range desired.
4. Wait for a time, t_NVS (minimum 10 μs).
5. Set the HVEN bit.
6. Wait for a time, t_PGS (minimum 5 μs).
7. Write data to the Flash address being programmed⁽¹⁾.
8. Wait for time, t_PROG (minimum 30 μs).
9. Repeat step 7 and 8 until all desired bytes within the row are programmed.
10. Clear the PGM bit⁽¹⁾.
11. Wait for time, t_NVH (minimum 5 μs).
12. Clear the HVEN bit.
13. After time, t_RCV (typical 1 μs), the memory can be accessed in read mode again.
NOTE
The COP register at location $FFFF should not be written between steps
5-12, when the HVEN bit is set. Since this register is located at a valid Flash
address, unpredictable behavior may occur if this location is written while
HVEN is set.
This program sequence is repeated throughout the memory until all data is programmed.
NOTE
Programming and erasing of Flash locations cannot be performed by code
being executed from the Flash memory. While these operations must be
performed in the order shown, other unrelated operations may occur
between the steps. Do not exceed t_PROG maximum, see 20.20 Memory
Characteristics.
1. The time between each Flash address change, or the time between the last Flash address programmed to clearing PGM
bit, must not exceed the maximum programming time, t_PROG maximum.
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
Freescale Semiconductor
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